Isolation of benzyl cellulose



Patented Mar. 25, 1930 UNITED STATES PATENT OFFICE.

EDUARD norm, or ELIBERFELD,

GERMANY, ASSIGNOR TO I. G. FARBENIND USTRIE or GERMANY No Drawing.Original application filed September 20, 1926, Serial No. 136,723, andin Germany ISOLATION or BENZYL CELLULOSE 1925.. Divided and thisapplication filedAugust 13, 1927. Serial No. 212,833.

In the benzylation of-cellulose the crude benzyl cellulose is producedas a tough, gumlike mass containing benzyl alcohol and ben- Zyl ether.

Hitherto, the working up of this crude product has been efi'ected byextracting the reaction mass with ligroin and the like, which dissolvebenzyl alcohol and benzyl ether, but not the benzyl cellulose.

On account of the above-mentioned consistency of the benzylated materialthis process is difiicult of execution, large quantities ofsolvent beingrequired in addition to'the operation of kneading and involving aconsiderable loss of time. Moreover by this means the benzyl celluloseis only obtained completely free from benzyl alcohol and benzyl etherwith the utmost difliculties.

The present invention concerns the production of benzyl celluloses of ahigh degree of purity and this new result is obtained with extreme caseby malaxating the tough, asty mass for a short time with any water-souble salt, preferably an alkalimetal-, or alkaline earth metal-, salt,until a moist friable mass becomes available, in which form the benzylcelluloses are most suitable for the extraction.

When this condition has been reached the benzyl alcohol and benzylether, but not the benzyl cellulose, are dissolved out quickly andeasily by means of a solvent, such as alcohol,

benzine and the like, according to one of the well known process, untilthe extraction li uid no longer contains any benz 1 alcohol or benzylether. Since the crude enzyl cellulose is distributed throughout themass in a finely divided form this extraction takes place in acompafratively short time. Thereupon the salt is washed out with waterand the benzyl cellulose is dried. It is thus obtained as a whitefiocculent product.

According to an alternative method of working, the salt-containing massis only extracted with solvent until, on washing out the certainquantity of .ed atthis stage. solvents such as alcohol,-

intermixed salt, a fiocculent product is obtained which no longersticks-together. This naturally still contains a product, however, 4benzyl alcohol and benzyl ether and the final extraction of these iseflect- This manner of working is accompanied by an economy in solvents.

The following vention:

Example 1.-1 kilogram of crude benzyl cellulose is well mixed withcommon salt (i. e., a commercial grade of sodium chloride) in amountseither equal or double by weight (or more or less) and then extractedwith benzene in an extraction apparatus until the outflowing extractionliquid no longer contains any benzyl alcohol or benzyl ether. Thereuponthe salt content of the mass is removed by washing with water.

Example 2.1. kilogram of crude benz l cellulose is malaxated with commonsalt 1n amounts either equal or double by weight (or more or less). Whenthe mass has assumed a uniform consistency, 1 liter of alcohol -is addedand the kneading is continued for about to hour, when the liquid is run0115'. If necessary the mass is extracted a sec- 0nd time with 1 literof alcohol, after which the salt content is completely washed out withwater and the final residues of benzyl alcohol and benzyl ether are thenremoved from the fiocculent product with spirits.

'The process can also be varied by alternately working with differentsolvents, for example first with benzine, then with ethyl alcohol, thenwith acetone and lastly with water. 1

The present application is a division of my co-pending application Ser.No. 136,723, filed Sept. 20, 1926.

I claim: 1. The improvement in the isolation of August 17, I

examples-illustrate my incontaining the same, which comprises admixingsaid crude reaction productswith common salt; extracting the resultingmixture with benzine, and removing the residual salt by means of washingwith water.

2. The improvement in the isolation of benzyl cellulose from crudereaction products containing the same, which comprises admixingtherewith common salt, alternately extracting the resulting mixture withbenzine, alcohol and acetone, and removing the residual salt by means ofwashing with water.

In testimony whereof, I afiix my signature.

EDUARD D6BR.

